Information for Hay and Forage Producers

Following is information about aminopyralid for anyone selling hay to horse owners or livestock farmers. Manure from animals fed hay or forage that contains aminopyralid has the potential to harm sensitive plants if that manure is then used as a fertilizer in gardens.

What is aminopyralid?

Aminopyralid is the active ingredient in Milestone®, Milestone VM, Milestone VM Plus, ForeFront® R&P, Chaparral, GrazonNext, Opensight and CleanWave herbicides. These herbicides are among the most effective for controlling and eliminating many rangeland and pasture weeds including thistles, ragweeds, knapweeds and star thistle. 

Manure that has been generated by animals grazing on grassland or hay treated with aminopyralid may contain residues of aminopyralid. After ingestion, aminopyralid takes three days to completely pass through an animal. Manure produced during those three days can only be used to fertilize rangeland, pasture grasses and wheat fields. There is no restriction on the use of manure produced by animals that have grazed for at least three days on untreated pasture or hay.

Aminopyralid should not be in alfalfa silage, as it would not have allowed that crop to grow.

How does this affect me?

  • You are advised to find out whether your suppliers have treated their grassland with an aminopyralid-containing herbicide before cutting it for hay. If they did, you must tell your customers about this and advise them of the restrictions for the use of any subsequent manure produced from the animals that eat the treated hay.
  • It is advisable to keep treated and untreated hay separate.

What Can I Do?

  1. Be informed.
  2. The presence of aminopyralid in hay and forage should be rare, but it is important to check if in doubt.
  3. Use Dow AgroSciences resources, such as this website, to inform and educate your suppliers and customers.
  4. Ask your hay or forage supplier if they sprayed their fields with aminopyralid herbicides such as Milestone. If so, inform your customers.
  5. Take appropriate action before selling or supplying your product.
  6. If your suppliers have used aminopyralid-containing herbicides on their grass, store treated and untreated hay separately.
  7. Inform your customers about the restrictions for any manure produced from the animals that eat treated forage, i.e., it must not be used to fertilize ground destined for a sensitive crop, such as potatoes or legumes.

Contact Dow AgroSciences

If If you have additional questions about hay or manure containing aminopyralid, please contact the Dow AgroSciences Customer Information Group at 1-800-992-5994 and select Option No. 4; or e-mail